Sample tubes are usually adopted to collect samples of blood and body fluid to be analyzed in medical equipments. The sample tubes are generally inserted into a sample rack, such that one sample rack can store a plurality of sample tubes, thus facilitating movement and storage of the sample tubes while improving testing efficiency. Many medical equipments adopt a combination of the sample rack and the sample tubes. The sample rack with the inserted sample tubes is directly conveyed into the equipments for sample analysis, thereby enabling simple and convenient operation of such equipments. Although various equipments have different ways of conveying the sample rack inside it, the purpose is to convey the sample rack by means of a moving shaft, such that each sample in the sample tube in the sample rack can be analyzed. It is required that, during the period of conveying, each sample tube can accurately reach the testing places without tilting, rolling or damaging.
At present, there are two main solutions of conveying the sample rack by the medical equipment: one is to move the sample rack up and down, and the other is to translate the sample rack in a guide groove. The latter solution requires the sample rack to move back and forth, where a positioning pin can be protruded to be inserted into a positioning hole in the sample rack and the sample rack can be driven to move by another shaft or other shafts. The translation solution requires a positioning hole disposed in the sample rack, and this leads to a high requirement on the location accuracy of the positioning hole. However, since manufacturing tolerance may affect the positioning accuracy of a moving shaft, the positioning pin, when being protruded, is likely to be pressed against the sample rack, rather than being successfully inserted into the positioning hole. In this case, the moving shaft may be stuck, or the sample rack may be tilted to cause splashed liquids.
Considering a power part of the moving shaft, a motor as a power source may be used to drive the moving mechanism when the medical equipments are electrically controlled. The motor can be a rotary motor, in which case rotary movement is required to be converted into linear movement. A motor which is capable of moving linearly may lead to a special structure, a high cost and a large size. On the other hand, the rotary motor requires an intermediate transmission mechanism, thus increasing equipment manufacturing cost and occupation space. Therefore, there are high design requirements on the structure of the intermediate mechanism, the size of the occupation space and the transmission accuracy.